UCU officials estimate that the new contracts would give Barnfield College some 30,000 extra teaching hours a year.

Administrators have refused to say what the majority of extra hours would be used for, but the union fears they could lead to redundancies, which the college has refused to rule out.

The union is calling on the college to set a clear cap on the number of teaching hours for staff each week and halt current plans to increase staff’s teaching loads, which include preparation, marking and administration work.

UCU regional support official, Shane Hall, said: “Staff here are stretched to their limits already and this gun-to-the-head diplomacy has pushed them to the edge.

“It is a ridiculous situation whereby a worker can agree and sign a contract of employment outlining their pay and conditions, and then whenever their employer wishes to change it they simply tell them to agree to the change or they’ll be dismissed.

“No employee should or would stand for that.

“We fear the college wants fewer staff to do more work, which will result in job losses. Industrial action is always a last resort but when people’s jobs are at risk, it’s important to make a stand.”

The UCU says most staff at Barnfield College already work above their contracted hours to get everything done. Officials believe an increase in teaching hours would leave staff having to work even more hours of unpaid overtime.

90% of UCU members who voted in a strike ballot backed the call for action in a row over changes to their contracts.